1. Field of the Invention
The present invention relates to an apparatus for removing residuary pollution from various substrates such as a semiconductor wafer, a glass substrate for a liquid crystal display, a PDP (Plasma Display Panel) substrate or a glass substrate and a ceramic substrate for magnetic discs.
2. Description of the Background Art
In a substrate processing system, an apparatus for removing remaining contaminants from a substrate is used. Such remaining contaminants may include reaction products generated on the substrate due to quality change of a resist. In most cases, the reaction products are an organic substance. For example, when dry-etching is effected on a thin film existing on the surface. of the substrate with the use of a resist film as a mask, reaction products are generated on the substrate. This reaction products need to be removed efficiently. In the following, this circumstance will be explained more concretely.
Manufacturing processes of a semiconductor device include a process in which a metal thin film such as aluminum or copper formed on a substrate such as a semiconductor wafer is subjected to etching by using a resist film as a mask to form wiring of semiconductor elements.
For example, as illustrated in FIG. 91A, electronic elements 8102 are formed on a semiconductor substrate 8101, and a metal film 8103 is formed thereon. This metal film 8103 is made of, for example, aluminum.
Further, a resist film 8104 is formed on the metal film 8103. This resist film 8104 is formed through the following processes: resist is applied to a top surface of the metal film 8103 to be dried thereon, the dried resist is selectively exposed by an exposing device in the form of a wiring pattern, and a developing liquid is supplied to the exposed resist to remove unnecessary portions therefrom. In this manner, only the necessary portions of the metal film 8103 are masked by the resist film 8103, and in the succeeding etching process, the necessary portions of the metal film 103 are allowed to remain without being etched.
Next, a dry-etching process such as RIE (Reactive Ion Etching) is carried out on the metal film 8103 masked by the resist film 8103 so that portions of the metal film 8103 that have not been masked by the resist film 8103 are etched and removed and the portions remaining without having been etched are allowed to form metal wiring 8106.
When the dry-etching is carried out as described above, reaction products 8105, derived from the resist film 8103, etc., accumulate on the sides of the metal wiring 8106, as shown in FIG. 91B.
In most cases, these reaction products 8105 are not removed in the succeeding resist-removing process, and tend to remain on the substrate 8101 as shown in FIG. 91C, even after the removal of the resist film 8104.
When the substrate 8101 is sent to the next process without removing such reaction products 8105, they tend to give adverse effects on the quality of the next process and thereafter; therefore, it is necessary to remove them before the next process.
In order to remove the reaction products 8105, in the conventional substrate processing apparatus, a plurality of process liquids, such as a remover liquid, an intermediate rinse liquid and deionized water, are successively supplied from respective nozzles while the substrate is being rotated. In the apparatus of this type, the following improvements have been demanded.
(1) Improvements in the Throughput
Here, it has been known that, when the remover liquid and deionized water are mixed, a phenomenon referred to as “pH shock” in which a strong alkali is generated, occurs, resulting in damages to the metal wiring.
For this reason, in the conventional method, in order not to directly mix the remover liquid and deionized water, an intermediate rinse liquid is supplied so as to once remove the remover liquid from the substrate, and deionized water is then supplied to the substrate so as to carry out a deionized water cleaning process.
In such a conventional technique, the intermediate rinse step takes a long time, resulting in adverse effects on the throughput.
Moreover, in the conventional technique, a large amount of intermediate rinse liquid is required in the intermediate rinse step, resulting in high costs.
(2) Improvements in the Temperature Control in Process Liquids
Conventionally, with respect to the remover liquid used in the removing process of these reaction products that have been generated through dry-etching, those liquids adapted to a room temperature have been generally used. However, in recent years, remover liquids, which exert an improved removing function on the removing products when used at high temperatures, have been developed.
In the case when such a high-temperature type remover liquid is used, the remover liquid is heated to a temperature in the range of approximately 50 to 80 degrees in Celsius by using a temperature-raising mechanism for the remover liquid, and the temperature of the remover liquid is controlled with high precision. In other words, when the temperature of the remover liquid to be supplied to the substrate varies, it becomes impossible to carry out the removing process of the reaction products with high precision. For this reason, the temperature control of the remover liquid needs to be carried out so as to always maintain the temperature of the remover liquid to be supplied to the substrate at a fixed temperature.
However, in such a substrate processing apparatus, during a non-processing period of time up to the start of the process on substrates in the next lot after substrates in the preceding lot have been processed, or during a non-processing period of time up to the start of the process on the next substrate after the process of a preceding substrate, the remover liquid tends to be cooled off inside pipes, etc., between the temperature-raising mechanism of the remover liquid and the remover liquid discharging section for discharging the remover liquid to the surface of the substrate, resulting in a failure to carry out the removing process of the reaction products with high precision.
(3) Improvements in Nozzles
In the conventional substrate processing apparatus of this type for removing the reaction products, the remover liquid is supplied to a fixed portion on the substrate. For this reason, there is a difference in the process quality between the fixed portion and the other portions, failing to maintain the in-plane uniformity of the substrate.
In particular, the remover liquids have such a characteristic that they exert the highest removing efficiency of the reaction products when used at the respective predetermined temperatures. For this reason, in the case when the remover liquid is supplied to the fixed portion of the substrate, it becomes difficult to maintain the in-plane uniformity of the substrate.
Further, the remover liquid supplying nozzle of such a conventional substrate processing apparatus is formed by a simple straight tube that is directed toward the substrate with its tip being open. For this reason, since the remover liquid hits the substrate in a dot form, it is difficult to maintain the in-plane uniformity in the process.
More specifically, the portion (referred to as a liquid arrival portion) at which the remover liquid hits the substrate in the dot form makes it possible to remove the reaction products in a comparatively short time, since a fresh remover liquid is always supplied thereto. However, the other portion (referred to as a liquid non-arrival portion) tends to have a slower process in comparison with the liquid arrival portion. In other words, there are deviations in the time required for completing the process on the surface of the substrate.
For this reason, in the conventional substrate processing apparatus, it is necessary to wait for the completion of the process in the liquid non-arrival portion in order to remove the reaction products from the substrate. However, in contrast, the remover liquid slightly has a corrosion effect on the metal film 8103, with the result that during the waiting time for the completion of the process on the liquid non-arrival portion, the corrosion might take place on the metal film 8103 in the liquid arrival portion to a degree exceeding a permissible range.
Here, with respect to the substrate cleaning device, a droplet-injection cleaning method, which uses a cleaning double fluids nozzle for strongly removing contaminants adhering the surface of the substrate, has been proposed.
FIG. 92 is a schematic drawing of a cleaning device in which the conventional cleaning double fluids nozzle is used. This cleaning device is provided with a cleaning cup 2051, a spin chuck 2052 for holding a substrate W inside the cleaning cup 2051, an electric motor 2053 for rotating this spin chuck 2052, a gas supplying means 2055 for supplying pressurized gas to the cleaning double fluids nozzle 2060 for discharging droplets onto the surface of the substrate W, and a liquid supplying means 2056 for supplying a pressurized liquid to the cleaning double fluids nozzle 2060. Moreover, a robot arm 2057 for holding and shifting the cleaning double fluids nozzle 2060 is installed.
FIG. 93 shows a cross-sectional view of the conventional cleaning double fluids nozzle 2060. The cleaning double fluids nozzle is provided with a first tube path 2061 through which gas is transmitted, and a second tube path 2062 the tip of which is allowed to penetrate the side wall of the first tube path 2061 from the outside of the first tube path 2061, and extended to the inside of the first tube path 2061 and through which a fluid is transmitted. The tip of the second tube path 2062 is extended in the same direction as the direction in which the first tube path 2061 is extended.
A substrate W is fixed to the spin chuck 2052, and rotated at a predetermined number of revolutions. Pressurized gas is supplied from a gas supplying means 2055 to the cleaning double fluids nozzle 2060, and a pressurized liquid is supplied from a liquid supplying means 2056 thereto, respectively. In the cleaning double fluids nozzle 2060, the gas and the liquid are mixed with each other so that the liquid is changed to droplets in the form of mist. These droplets are accelerated by the gas flow inside the first tube path 2061, and discharged from the tip of the first tube path 2061. The atomized droplets thus discharged are made to collide with the surface of the substrate W, thereby removing the contaminants adhering to the surface of the substrate W.
However, in the above-mentioned cleaning device, the gas and the liquid are mixed inside the cleaning double fluids nozzle 2060. Therefore, when the flow rate of one fluid is attempted to be changed independently of the flow rate of the other fluid, the latter is also changed since the respective pressures interfere with each other inside the first tube path 2061.
In other words, in the case when the gas flow rate is increased so as to increase the cleaning strength, since the pressure of the gas inside the first tube path 2061 increases so that the flow rate of the liquid supplied from the second tube path 2062 is suppressed. Consequently, the droplets to be discharged from the tip opening of the nozzle of the double fluids nozzle 2060 tend to have cleaning strength different from the initial cleaning strength due to the suppressed liquid flow rate.
Consequently, fine particles such as dusts and slurries tend to remain on the surface of the substrate W, resulting in a serious problem of a reduced yield in the manufacturing process of the semiconductor device.
Moreover, in the above-mentioned cleaning device, since the gas and the liquid are mixed inside the cleaning double fluids nozzle 2060, dusts are generated because irregularities on the inner wall of the nozzle 2060 are cut. The dusts may be also generated during the mixing operation. The substances resulting from the dried liquid and adhering to the inside of the nozzle 2060 are taken off by the flow in the nozzle.